Industrial Production: How are Springs Made?
Springs are widely used in our lives, from industrial machinery and hardware products, agricultural and construction machinery, and even other consumables such as mattresses. These coiled springs have strong performance and provide good tension and contraction force. High carbon steel springs still play an important role in the low-end industrial and consumer fields due to their economy and sufficient mechanical properties.
Although we all know about springs, how are springs made? Here, we will discuss the manufacturing process of high carbon steel springs.
How are Springs Made?
If the diameter of your raw material wire matches the spring, you only need a spring machine; if the diameter of your raw material wire is larger than the wire diameter of the spring, this process requires the intervention of other machines, that is, the high carbon steel straight wire drawing machine, which is the initial machine to draw the raw material wire diameter to the wire diameter you need, and then use the spring machine to make the spring.
1. Raw material preparation
High-carbon steel wire is usually supplied as wire rod (hot-rolled wire) with a carbon content between 0.6% and 1.0%. It has high strength and elasticity, but it needs to be drawn and heat-treated to achieve ideal properties.
2. Wire Drawing
Purpose: To draw the thick steel wire to the required diameter, improve the surface finish, and mechanical properties.
Equipment: wire drawing machine (wet or dry drawing).
Steps:
Pickling: Remove the oxide scale on the surface of the wire rod (using hydrochloric acid or sulfuric acid).
Phosphating/Saponification: Form a lubricating layer on the surface of the steel wire (reduce drawing friction).
Drawing:
Rough drawing (large diameter reduction) → Medium drawing → Fine drawing (final diameter, such as Φ0.5mm~Φ5mm).
Multiple drawing passes, each pass reducing the diameter by about 10%~20%.
Annealing (intermediate annealing):
If the work hardening is severe, recrystallization annealing (650~750℃) is required in the middle of the drawing process to restore plasticity.
Wire Drawing Processing:
3. Annealing
Purpose: To eliminate internal stress after drawing, improve plasticity, and facilitate subsequent winding.
Process:
Spheroidizing annealing (suitable for high carbon steel):
Heat to 740~780℃, keep warm and then slowly cool (furnace cooling) to spheroidize carbides and improve cold formability.
Bright annealing (protective atmosphere to prevent oxidation).
4.Spring Coiling
Equipment:
Automatic spring machine (CNC spring coiling machine): used for mass production, can control pitch, outer diameter, number of turns, etc.
Steps:
Select mandrel: mandrel diameter ≈ spring inner diameter + wire rebound (empirical formula: mandrel diameter = spring inner diameter × 0.8~0.9).
Adjust spring machine parameters:
Feeding speed, pitch (stretch springs need to reserve spacing), and grinding of both ends.
Winding:
High carbon steel wire has high hardness, and it is necessary to ensure that there are no cracks during winding (otherwise, it is easy to break later).
How are Springs Made?
6.Surface treatment
Purpose: Anti-rust and improve fatigue strength.
Shot peening: Use steel shots to hit the surface to generate compressive stress and improve fatigue life.
Plating/phosphating: zinc plating, nickel plating, or phosphating for rust prevention.
Coating: epoxy resin or Dacromet for corrosion protection.
7.Testing and calibration
Purpose: Anti-rust and improve fatigue strength.
Elasticity test: compress/stretch to the specified deformation and check whether it is qualified.
End surface grinding (if necessary): Use a double-end surface grinder to ensure the verticality of the spring.
Fatigue test (high-end application): simulate long-term use.
8.Key Considerations
Material selection:
Ordinary spring: 65Mn (high cost performance).
High fatigue requirements: 50CrV, 60Si2Mn (automobile suspension spring).
Corrosion resistance: 304 stainless steel or piano wire (SWP).
Drawing control:
Too high a reduction rate can easily lead to wire breakage, so the number of passes needs to be reasonably allocated.
Heat treatment process:
Quenching temperature is too high → coarse grains; too low → insufficient hardness.
Insufficient tempering → high brittleness; excessive tempering → decreased elasticity.
Winding skills:
High carbon steel wire has a large rebound, so the mandrel diameter needs to be adjusted appropriately.
Spring Wire Application:
Springs (such as 65Mn, 70# steel, T8A, etc.) are widely used in high-stress and high-frequency working environments due to their high strength, elasticity, and excellent fatigue resistance.
Main application areas:
Automotive industry: suspension springs (65Mn), clutch diaphragm springs (70# steel), and engine valve springs (T8A) require impact resistance and long life.
Mechanical manufacturing: punch buffer springs, valve control springs, bearing high-frequency loads.
Home appliances and electronics: washing machine shock absorber springs, electrical switch reset springs, requiring precise elasticity.
Military and aerospace: gun recoil springs, satellite antenna deployment mechanisms, relying on high reliability and fatigue resistance.
Advantages: low cost, high elastic limit, after quenching + tempering and surface treatment, the life is significantly improved.
